For the past 4 to 5 years I have been water washing my biodiesel with a compressor and I am reasonably happy with it. I say reasonably because water washing, although I seem to have now got it to a fine art is a bit of a pain, extra time, extra heat, then the drying cycle takes longer etc etc.
So on the last batch I de-methed, settled 24 hours, extracted every drop of glycerol that had dropped out of the bottom line, re-heated only to 30degs, washed with pure glycerine (7th time used) to extract any soap, left it 24 hours again, ran off all the glycerine and let it settle.
Over the next 3 days about 3" of glycerine came out of the bottom 1" pipe.
The next day 4mls came out. The day after none came out and the day after about 2 mls came out.
At this point I heated it to dry it with the turbo dryer, an 8 hour cycle, slowly up to 65degs and down to 40degs.
It was left overnight to rest. The next day I opened the bottom valve again and ran out my usual small beaker full and still got about 3mls of glycerol.
So after 8 days of settling there was still a very small amount of glyc dropping out. The 3mls or so in a 200 batch is about 15ppm. Should I be worried by this, is it normal, what do other people get when settling. I'm still not happy, this doesn't happen with water washing. The soap in this batch is about 10ppm.
Could a centrifuge be the answer if using the settling method.
Here are some pictures of the 50/50 test and the small beaker of bio extracted with the small layer of glycerine.
